Refrigerators or refrigerator appliances generally include a cabinet that defines a chilled chamber. The chilled chamber is commonly cooled with a sealed system having an evaporator. One problem that may be encountered with existing refrigerator appliances is inefficient defrosting of the evaporator. For example, when the evaporator is active, frost can accumulate on the evaporator and thereby reduce efficiency of the evaporator. One effort to reduce or eliminate frost from the evaporator has been to utilize a heater, such as an electrical heater, to heat the evaporator, e.g., when the evaporator is not operating.
Utilizing an electrical heater to defrost an evaporator can pose certain challenges. For example, certain refrigerators utilize a flammable refrigerant within the sealed system. In such systems, a surface temperature of the heater is generally limited to a temperature well below the auto-ignition temperature of the flammable refrigerant. However, the evaporator generally requires a certain power output from the heater to suitably defrost. Moreover, it is possible that a portion of electrical heater may fail. As an example, in the case of a single or dual glass tube heater, one or more of the glass tubes may crack or rupture. If such a crack or rupture occurs, refrigerant could be exposed to temperatures in excess of the refrigerant's auto-ignition temperature.
Accordingly, a heating assembly with certain safety features would be useful. In particular, a heating assembly that is configured to detect and respond to damage suffered by the heating assembly would be useful. For instance, it would be advantageous to detect a crack or rupture in a tube of a heater assembly. Moreover, it may also be useful to have a refrigerator appliance with a heating assembly for defrosting an evaporator of the refrigerator appliance, while also operating at a surface temperature well below an auto-ignition temperature of a flammable refrigerant within the evaporator.